GENETIC DIVERSITY AND ECOLOGICAL DISTRIBUTION OF
PHASEOLUS V U L G A R I S (FABACEAE) IN
NORTHWESTERN SOUTH AMERICA 1
DANIEL G. DEBOUCK, ORLANDO TORO, OSCAR M. PAREDES,
WILLIAM C. JOHNSON, AND PAUL GEPTS2
Debouck, Daniel G. (International Board for Plant Genetic Resources, Via delle Sette Chiese
142, Rome, Italy), Orlando Toro (Centro Internacional de Agricultura Tropical, Apartado a~reo
6713, Cali, Colombia), Oscar M. Paredes, William C. Johnson, and Paul Gepts (Department
of Agronomy and Range Science, University of California, Davis, CA 95616-8515). GENETIC
DIVERSITY AND ECOLOGICAL DISTRIBUTION OF PHASEOLUS VULGARIS (FABACEAE) IN NORTHWESTERNSOUTH AMERICA. Economic Botany 47(4):408-423. 1993. Our goal was to investigate
in more detail wild and cultivated common bean (Phaseolus vulgaris) accessions from northwestern South America (Colombia, Ecuador, and northern Peru) because prior research had
shown this region to be the meeting place of the two major gene pools (Middle American and
Andean) of common bean. Explorations were conducted tn these countries to collect additional
materials not represented in germplasm collections. It was possible to identify wild common bean
populations in Ecuador and northern Peru, where they had never been described before. In
addition, we were able to extend the distribution of wild common bean in Colombia beyond what
was known prior to this study. In all areas, the wild common bean habitat had suffered severely
from destruction of natural vegetation. In Colombia, wild common beans were found on the
Eastern slope of the Andes (in continuation of its distribution in Venezuela), whereas in Ecuador
and northern Peru they were found on the western slope of this mountain range. This geographic
distribution was correlated with an ecological distribution in relatively dry environments with
intermediate temperatures (known as "dry mountain forest "'). Isozyme and phaseolin seed protein
analyses of the northern Peruvian and Ecuadoran wild populations showed that they were intermediate between the Middle American and A ndean gene pools of the species. Phaseolin analyses
conducted on landraces of the Upper Magdalena Valley tn Colombta showed that Andean domesticates were grown at a higher altitude than Mzddle American domesticates suggesting that
the former are adapted to cooler temperatures. Our observations and results have the following
consequences for the understanding and conservation of genetic diversity in common bean and
other crops: 1) Our understanding of the distribution of the wdd relative of common bean (and
other crops) is imperfect and further explorations are needed to more precisely identify and rescue
wdd ancestral populations; 2) For crops for which the wild ancestor has not yet been identified,
it may be worthwhile to conduct additional explorations m conjunction with genetic diversity
studies at the molecular level to guide the explorations," 3) Our study shows the benefit for more
efftcwnt germplasm conservation which can be derived from the dynamw interplay between field
explorations (and other conservation operations) and molecular analyses to determine genetic
distances and diversities; 4) The intermediate materials identified in northern Peru and Ecuador
may have basic importance to understand the origin of the common bean and an applied role
as a bridge between the Middle American and Andean gene pools; and 5) The differential
adaptation to temperature of the two major cultwated gene pools may help breeders select
genotypes based at least partially on their evolutionary origin.
Diversidad gen6tica y distribuci6n ecol6gica de Phaseolus vulgaris (Fabaceae) en el noroeste de
Suram6rica. Nuestro objectivo rue investigar rods detalladamente las poblaciones silvestres y
cultivadas del frfjol comCm (Phaseolus vulgaris) del noroeste de Suram~rica (Colombia, Ecuador,
Received 13 April 1993; accepted 22 July 1993.
2 D G D is now at IBPGR, %CIAT, Apartado a6reo 6713, Cali, Colombia. Reprint requests should be addressed
to PG.
Economic Botany 47(4) pp. 408-423. 1993
9 1993, by The New York Botanical Garden, Bronx, NY 10458 U.S.A.
1993] DEBOUCK ET AL.: P H A S E O L U S VULGARIS IN NORTHWESTERN SOUTH AMERICA
409
y PerfO porque investigaciones previas habfan ense~ado queen esta regi6n se encuentran los dos
acervos genOttcos mayores (Mesoamertcano y Andino) de la especie. Nuevos materiales que no
estaban representados arm en bancos de recursos gen~ttcos fueron recolectados en los tres parses
mencionados. Se encontraron poblaciones sdvestres en Ecuador y el norte de Peril donde nunca
se habfan reportado antes. Adem~s, se extendi6 la distribuci6n del frfjol stlvestre en Colombia
m ~ all6 de lo que se conocfa anteriormente. En todas las ~reas, el habitat del frfjol silvestre
habia padecido fuertemente de la destrucct6n de la vegetacirn natural En Colombia, se encontraron formas silvestres en la Corddlera Oriental (a contmuacirn de su distribuci6n en Venezuela)
mwntras q u e e n Ecuador y el norte peruano fueron encontradas en la ladera occidental de la
Cordillera. Esta distribuci6n geogrffica estaba correlactonada con una distribuci6n ecol6gica en
ambientes relativamente secos con temperaturas intermedias (conocidos como "bosque seco
montano"). An6lisis de isoenzlmas y de faseolinas, la proteina mayor de la semilla, mostraron
que las poblaciones sdvestres de Ecuador y del norte de Per~ eran intermedias entre los acervos
Mesoamericano y Andino. Anrhsis de faseohna en vartedades criollas del Alto Magdalena en
Colombia ense~aron que las variedades de or{gen andino se cultivaban a m(ts altitud que las
variedades mesoamericanas. Esta observaci6n sugwre que en promedio variedades andinas son
adaptadas a temperaturas mrs frescas. Se proponen las siguientes conclusiones: 1) E l conocimwnto de la distribucirn del ancestro silvestre del frOol comfm (y de otros culuvos) es incompleto
y se preclsan otras recolecclones para tdentificar y salvar poblactones silvestres; 2) En cultivos
para los cuales todavfa no se ha encontrado el ancestro silvestre, se recomienda recolecciones
adicionales junto con anrlisis de diversidad gen~ttca al nivel molecular para guiar las recoleccrones; 3) Este estudio demuestra la tmportancia para la conservacl6n de recursos genOticos de
una interacclrn din(tmwa entre recolecciones (y otros pasos en le conservacl6n) y andlisis al nivel
molecular para determmar distanclas y diverstdades gen~ticas; 4) Los matertals intermedios que
se identtficaron en Ecuador y el norte de Perft podrfan tener un papel en la determinaci6n del
origen de la especie y como puente entre los dos acervos; y 5) La adaptaci6n diferencial a la
temperatura de los dos acervos cultivados mayores puede ayudar a los mejoradores a seleccionar
genotipos con base parcialmente a su ortgen evolucionario.
Key Words: common bean; Phaseolus vulgaris; ecological adaptation; germplasm exploration;
isozymes; phaseolin.
Common bean (Phaseolus vulgaris L.) was domesticated in the New World probably some
8000-10 000 years ago from a wild ancestral form
distributed in the highlands of what is now Latin
America between northern Mexico and northern
Argentina (McBryde 1947; Burkart and Briicher
1953; Kaplan 1965; Lynch et al. 1985; Kaplan
and Kaplan 1988; Gepts and Debouck 1991).
The cultivated gene pool of common bean (P.
vulgaris L.) consists of two major geographic entities, which can be distinguished by their morphology (Evans 1976; Singh et al. 1991), phaseolin seed protein electrophoretic type (Gepts et al.
1986; Gepts and Bliss 1986; Koenig, Singh, and
Gepts 1990), isozymes (Sprecher 1988; Singh,
Nodari, and Gepts 1991), RFLPs for mitochondrial DNA (Khairallah, Adams, and Sears 1990)
and nuclear DNA (Nodari et al. 1992), and the
presence of occasional F, hybrid weakness (Shii
et al. 1980; Singh and Gutirrrez 1984; Gepts and
Bliss 1985). Analyses in wild ancestral beans of
phaseolin (Gepts et al. 1986; Gepts and Bliss
1986; Koenig, Singh, and Gepts 1990), isozymes
(Koenig and Gepts 1989), and F~ hybrid weakness (Koinange and Gepts 1992) indicate that
this divergence in the cultivated gene pool is due
to multiple domestications from an already diverged wild ancestor in Middle America and the
Andes.
Isozyme analyses by Koenig and Gepts (1989)
more specifically showed that the wild populations of the Middle American gene pool extended
from northern Mexico to Colombia, whereas the
Andean populations ranged from southern Peru
to northern Argentina. Until a few years ago, no
wild beans had been reported from the region
comprised by southern Colombia, Ecuador, and
northern Peru. One wild accession resulting from
a recent exploration in northern Peru by Debouck (1986) appeared, however, to be intermediate between the Middle American and Andean gene pools based on isozyme (Koenig and
Gepts 1989) and phaseolin data (Koenig, Singh,
and Gepts 1990). This observation suggested that
it might be worthwhile to collect additional wild
beans in this region, if any were present, and
determine their relationship with other wild bean
populations. In addition, phaseolin data of cultivated beans showed that Colombia and, to a
lesser extent, Ecuador, represent a meeting place
410
ECONOMIC BOTANY
T A B L E 1.
[VOL. 47
IDENTIFICATION, G E O G R A P H I C ORIGIN, A N D ALTITUDE OF COLLECTION OF WILD PHASEOLUS
VULGARIS FROM E C U A D O R A N D N O R T H E R N P E R U ANALYZED FOR ISOZYMES AND PHASEOLIN.
Accession
Geographic ongm
CIAT
number
Explorer's
number
Country
G23579
G23580
G23581
G23582
G23724
G23726
G21244
G21245
G23583
G23584
G23585
DGD2762
DGD2763
DGD2765
DGD2769
DGD2881
DGD2889
DGD 1956
DGD 1962
DGD2788
DGD2854
DGD2855
Ecuador
Ecuador
Ecuador
Ecuador
Ecuador
Ecuador
Peru
Peru
Peru
Peru
Peru
for the Middle American and Andean cultivated
gene pools (Gepts and Bliss 1986). Analyses of
common bean germplasm from the two major
gene pools growing in the same region might tell
us whether members of these gene pools have
differential environmental adaptations.
In this article, we describe the geographical
location and ecological adaptation of wild beans
collected recently in northwestern South America (Colombia, Ecuador, and northern Peru). We
analyze the relationship of these wild beans to
other wild beans based on isozyme and phaseolin
data. We also discuss the possible differential
adaptation to temperature of cultivated germplasm from Middle America and the Andes in
this area.
MATERIALS AND METHODS
COLLECTION OF PLANT MATERIAL
Materials considered in this study were collected during seven explorations: two in Colombia (1985, 1990), two in Ecuador (1989, 1990),
and three in Peru (1985, 1986, 1990). They included 12 wild and 36 cultivated accessions (Tables 1 and 2; Fig. 1) At each collection site, information was gathered about the location (site
name, municipality, province or department), its
altitude and exposure, soil characteristics, morphological traits (e.g., flower color, growth habit),
presence of diseases and pests, vernacular names,
and utilization by local people. For each site, a
seed sample was taken, half of which was deposited with the respective national agricultural
research programs (Instituto Colombiano Agropecuario in Colombia, Instituto Nacional de Investigaciones Agropecuarias in Ecuador, and In-
Location
Gir6n, Azuay
Glr6n, Azuay
Gir6n, Azuay
Huigra, Chimborazo
Eloy Alfaro, Loja
Pallatanga, Chimborazo
San Pablo, Cajamarca
San Miguel, Cajamarca
Huancabarnba, Piura
Huancabamba, Piura
Chota, Cajamarca
Altitude
(m)
1990
1930
1600
1710
960
1610
2020
1790
920
1100
930
stituto Nacional de Investigaci6n Agraria y
Agroindustrial in Peru) and the other half with
the Genetic Resources Unit of the Centro Internacional de Agricultura Tropical (Cali, Colombia) or the Western Regional Plant Introduction
Station of the United States Department of Agriculture (Pullman, Washington, U.S.A.). For
each wild bean collection, herbarium samples
were deposited with a herbarium in the respective countries of origin (for Colombia: Herbario
Nacional Colombiano (COL) in Bogota; for Ecuador: Pontificia Universidad Cat61ica del Ecuador (QCA) in Quito; and for Peru: Universidad Nacional Mayor de San Marcos de Lima
(USM) in Lima) and herbaria in other countries
(for the USA: University of Michigan (MICH)
in Ann Arbor, Smithsonian Institution (US) in
Washington; for Belgium: Jardin Botanique National de Belgique (BR) in Meise).
ANALYSIS OF PHASEOLINAND
ISOZYME VARIABILITY
For each accession, five seeds were analyzed
by electrophoresis. Each electrophoretic run included a Middle American (cultivar ICA-Pijao)
and an Andean (cultivar California Dark Red
Kidney) control. In addition, accession
DGD 1962 (G21245), collected in northern Peru
and analyzed previously for phaseolin type (Koenig, Singh, and Gepts 1990) and isozyme profile
(Koenig and Gepts 1989), was also included for
direct comparison with other accessions of that
region. Phaseolin electrophoretic type was determined by one-dimensional polyacrylamide gel
electrophoresis as described in Gepts et al. (1992).
Isozyme analyses were conducted as described
1993] DEBOUCK ET AL.: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
T A B L E 2.
411
IDENTIFICATION, GEOGRAPHIC ORIGIN, A L T I T U D E OF COLLECTION, PHASEOLIN TYPE AND SEED
SIZE OF CULTIVATED PHASEOLUS VULGARIS FROM COLOMBIA,
100seo- Seed
hn weight
type
(g)
Pha-
Explorer's
number
DGD2901
DGD2905
DGD2907
DGD2913
DGD2914
DGD2923
DGD2927
DGD2942
DGD2950
DGD2951
DGD2952
DGD2953
DGD2954
DGD2955
DGD2956
DGD2957
DGD2958
DGD2959
DGD2960
DGD2962
DGD2963
DGD2964
DGD2965
DGD2966
DGD2967
DGD2968
DGD2969
DGD2970
DGD2971
DGD2972
DGD2973
DGD2974
DGD2976
DGD2978
DGD2980
DGD2984
Location of ongm
Alutude
(m)
Inza, Cauca
El Patico, La Plata, Huila
Monserrate, Garzrn, Huila
Villa Fatima, Pitalito, Huila
Villa Fatima, Pitalito, Huila
E1 Palmito, Pacarni, Tesalia
El Cedralito, Vegalarga, Neiva, Huila
Bocas de Anamichu, Rio Blanco, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolirna
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Rlsalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tolima
Risalda, Chaparral, Tohma
Villa Hermosa, San Antonio, Tolima
Vdla Hermosa, San Antonio, Tolima
Altos de Playa Rica, San Antonio, Tolima
E1 Rosario, Tena, Cundinamarca
1660
1110
1040
1520
1520
1600
1520
760
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
1700
2120
2120
2120
2120
2120
2120
2120
2120
2120
1840
1840
1200
1540
Name
Comfin
Chiquito
Vagabundo, Sinverguenza
Frijol de jardln
Frijol de tierra
Frijol repelente, Rochela
Rochelas
Cejudo, Cejudito
Boca de sapo
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Revoltura
Culatefio
Vagabundo
Huevo de Pinche
Tempraneros
Revoltura
Revoltura
Revoltura
Revoltura
Vagabundo
Cejudo
Balin
Huevo de Pinche
Chinchefio
Tabla roja
Caregato, Pielroja
in Koenig and Gepts (1989), Singh, Nodari, and
Gepts (1991), and Gepts et al. (1992). Isozyme
frequencies were analyzed by principal component analysis using PROC P R I N C O M P of SAS
(1988).
RESULTS
GEOGRAPHIC AND ECOLOGICAL
DISTRIBUTION OF WILD P. VULGARIS IN
NORTHWESTERN SOUTH AMERICA
The geographic distribution of wild c o m m o n
bean in northern South America is located in the
Andes m o u n t a i n range and consists of three dis-
T
S
S
S
S
S
S
T
T
T
T
T
T
T
T
T
S
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
S
S
T
S
54.5
25.3
20.2
17.8
20.9
29.0
27.3
53.5
47.0
58.0
43.8
54.6
33.5
32.8
45.4
39.5
38.0
34.5
48.0
34.3
35.0
57.6
49.1
62.5
58.9
62.1
59.0
55.5
45.7
59.9
51.2
83.0
24.0
28.0
48.3
25.1
continuous regions. A first region includes wild
c o m m o n bean populations from western Venezuela (states of Mrrida, Portuguesa and Trujillo)
(Berglund-Briicher 1967; Briicher 1988) down to
central Colombia (Departments of Cundinamarca and Boyacfi) (Gepts and Bliss 1986, and
present results). A second region includes wild
P. vulgaris populations distributed from western
Ecuador (provinces of Chimborazo, Azuay and
Loja; Debouck, Castillo, and Tohme 1989 and
present results) down to western Peru (Department of Cajamarca; Debouck 1986 and present
results). The third region (western La Libertad
412
ECONOMIC BOTANY
90"W
85"W
80"W
Capt~
'
, PANAMA
vX..,"
[VOL. 47
75"W
70"W
!
i "~
~ ~
1-x-'~J
\
.
...........
10"N
-;*"
a
#
.
,' COLOMBIA
,"
4
t
,/
0"
ECUAD~
5"S
~00_~
~
,
_
~
10"S
i
Fig. 1. Location of wild bean populations collected and analyzed in this study in relation to the distribution
of the subhumid low montane forest and the continental divide.
Department in Peru) constitutes a transition zone
in which the distribution of wild common bean
switches from the western slopes of the Andes
to the central (upper Marafion) and eastern side
of the Andes. For reasons that will be discussed
later on, we will consider that part of the distribution range south of approximately 7040 '
Southern latitude as belonging to the Southern
Andes. In the following paragraphs, we will consider more specifically the geographic distribu-
tion of each of the three disjunct areas in the
northern Andes, and, subsequently, their ecological attributes.
GEOGRAPHIC DISTRIBUTION
Distribution in Venezuela
Wild common beans have been reported from
the states of M6rida, Portuguesa, T~tchira and
Trujillo in the western Andes of Venezuela (Berg-
1993] DEBOUCK ET AL.: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
lund-Briicher 1967). According to this author,
they might also be present in the state of Lara.
Distribution in Colombia
First records for the presence of wild P. vulgaris in Colombia were also given by the Briichers who after exploring Venezuela found them
in the neighboring Colombian state of Norte de
Santander (Berglund-Briicher and Briicher 1976).
Later on, seed samples were provided by a French
entomologist, Dr. Bernard Leroi of the University of Tours, France, who collected bruchids and
their host plants in the department of Cundinamarca in 1982 (see Gepts and Bliss 1986; Toro,
Tohme, and Debouck 1990).
Collection No.
Province, place
#13 Cundinamarca, Ubaque,
Ubaque
# 14 Cundinamarca, Ubaque,
Ubaque
#15 Cundinamarca, Macheta,
Resguardo
#22 Cundinamarca, Choachi,
Maza
#24 Cundinamarca, Manta,
Monte Grande
#28 Cundinamarca, Tena, Tena
#47 Cundinamarca, Manta, Palo
Gordo
#111 Cundinamarca, Ubaque,
Ubaque
Altitude
(m)
1750
valleys of Rio Pamplonita and Rio T~chira
(Berglund-Briicher and Briicher 1976). Another
valley worth exploring might be the one of Rio
Margua. In Boyac~, from where it has not yet
been reported, it could be present in the valleys
of Rio Garagoa, upper Rio Lengupa, Rio Chicamocha and Rio T~mara. In Cundinamarca,
most of the potential valleys have been explored
on the eastern side of Santef6 de Bogoth (upper
Rio Negro and tributaries). On the western side,
an exploration of the Rio Bogot~ valley has resuited in the identification of a few populations
(counties of Tena, La Mesa, E1 Colegio). Additional valleys worth visiting there would be the
ones of the upper Rio Seco and Rio Negro. Explorations in central (Tolima, Risaralda, Valle)
and southern Colombia (Cauca, Huila, Narifio)
have so far failed to disclose populations of wild
common bean (Debouck, personal observations
in 1977, 1985, 1989, 1990).
1900
1900
1900
1600
1560
1900
1900
Distribution in Ecuador
Six populations of wild common bean have
been found so far in this country. They were
located in inter-andean valleys on the western
side of the Andes (Debouck 1989a, 1990b) and
not on the eastern side as predicted elsewhere
("P. aborigineus has not been reported yet from
Ecuador. Its presence may be expected in the
subtropical mountain forest on the eastern slopes
of the Andes," Briicher 1988:204). These populations are:
Collection No.
Province, place
These findings were extended with the discovery of three additional populations west of Bogat~t (Debouck 1990a), as follows:
#2762 Azuay, Sta. Isabel, Lentag
#2769 Chimborazo, Pepinales
Collection No.
#2865
#2881
#2882
#2889
Province, place
#2981 Cundinamarca, Tena, El Rosario
#2983 Cundinamarca, Tena, El Rosario
#2985 Cundinamarca, Tena, El Rosario
413
Altitude
(m)
1500
1530
1550
Pending further explorations, the distribution
of wild P. vulgaris in Colombia represents the
continuation of the range documented for Venezuela. In the border department of Norte de
Santander, wild common bean was found in the
Chimborazo, Alausi, Capsol
Loja, Macara, Cienegos
Loja, C61ica, Mullunama
Chimborazo, PaUatanga,
Florida
Altitude
(m)
1990
20901410
1870
960
1390
1610
The northernmost populations of wild P. vulgaris in Ecuador are located in the Chimborazo
province in two valleys oriented SW-NE (one in
the Rio Pangor valley and the other in the Rio
Atapo valley). These valleys are protected from
humid winds coming from the Pacific Ocean.
Wild beans were also found in the upper Rio
Jubones and Rio Rircay valleys in the province
414
ECONOMIC BOTANY
of Azuay. The southernmost populations of wild
common bean in Ecuador are found in the province of Loja in the upper Rio Catamayo and Rio
Macar~ valleys. Explorations in two different
years in northern Ecuador have failed to reveal
the presence of wild common bean populations
there, presumably because of the severe deforestation and destruction of natural vegetation and
its replacement by intensive agriculture. There
is, however, a slight possibility of finding wild
common bean in the upper valley of the Rio Mira
(provinces of Imbabura and Carchi), precisely
around Pimampiro, Bolivar and Cahuasqui.
[VOL. 47
This distribution on the western slope of the
Andes probably ends at the Rio Chicama (approxim. 7040' S. Lat.). An intensive search made
in 1989 in the Santa valley did not reveal any
population of wild common bean. Many of the
original sites were threatened because of overgrazing, excessive burning and cutting down of
natural thickets, fruit plantations and even coffee
(although with poor adaptation). Additional
places worth exploring would include the valleys
of Rio Chancay and Rio Chicama.
ECOLOGICAL FEATURES
Distribution in Peru
Six populations of wild common bean have
been discovered so far in northwestern Peru (Debouck 1986, 1989b), as follows:
Collection No.
Province, place
Altitude
(m)
#1956 Cajamarca, San Pablo, San2020
gal
#1962 Cajamarca, San Miguel, La
1740
Conga
#2788 Piura, Huancabamba, Sta.
920
Rosa
#2854 Piura, Huancabamba, Pasaya- 1100
pampa
#2855 Cajamarea, Chota, Fila Ca930
shupe
#2858 Cajamarca, Chota, Toc1250
moche
The distribution range apparently starts in the
upper valley of Rio Canchaque, a tributary of
the Rio Piura, in west-central Huancabamba
province (5~
Lat.). Wild common bean might
also be found in the province of Ayabaca bordering Ecuador, as a continuation of populations
found in the province of Loja (Debouck 1990b,
and present results), but field checks are still necessary. Additional populations were found in the
upper valley of the Rio Olmos in the extreme
south-east of the Department of Piura. Wild P.
vulgaris was also collected in the upper valley of
Rio de la Lethe in the western part of the Chota
Province, in Cajamarca. It was found on the upper slopes of Rio San Miguel valley, a tributary
of the Rio Jequetepeque, in the provinces of San
Pablo and San Miguel in southern Cajamarea
(although at higher altitudes than in Piura).
Venezuela
Wild common bean was described as a vine
in the cloudy montane forest ('Wolkenwald-Region': Berglund-Briicher 1967). However physical characteristics (altitude, rainfall, temperature) and the lists of species frequently found
together with wild P. vulgarissuggest that its habitat is more accurately described as the bosque
seco montano bajo (lower altitude dry forest) and
perhaps the driest habitats of the bosque hfimedo
montano bajo (lower altitude humid forest) (Ewel,
Madriz, and Tosi 1976).
Columbia
The following genera were observed at the collection sites: Cecropia sp., Psidium sp., Myrtus
sp., Ipomoea sp., Lantana sp., Bryophyllurn sp.,
and several species of annual Compositae and
Gramineae. Judging from vegetation aspect and
extrapolating from nearby climatological stations, one could expect 800-1500 m m rainfall/
year with driest periods around January and August (Anonymous 1982). The vegetation type is
somewhat intermediate between the bosque seco
premontano and bosque hftmedo premontano
(Anonymous 1988), that is humid variants of the
dry montane forest, and is heavily modified because of grazing and coffee plantations (Anonymous 1988; Espinal 1965; and current observations). The mean temperature is estimated of
18-24~ (Anonymous 1988). Soils derived from
andesites and metamorphic schists were observed at the collection sites. As stated above,
explorations in southern Colombia (especially
Narifio) have failed so far to disclose populations
of wild common bean, most likely because of the
high altitudes at which the bosque seco premontano occurs there (see Fig. 1).
1993] DEBOUCK ET AL.: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
415
Fig. 2. •iew•fthec•••ecti•nsite•fwi•dPhase••usvulgarisaccessi•nDGD2769(G23582)nearPepina•es•
on the road to the town of Huigra, Department of Chimborazo, Ecuador. a) Photographic view; b) Drawing
showing the distribution of wild bean populations between 1400 and 2000 m exclusively along steep roadsides
(triangles) and surrounded by fields, among them bean fields (circles). The asterisk shows the location of the
type specimen of P. rosei.
Ecuador
Peru
All populations identified so far in Ecuador
were found in vegetation types classified as 8 and
9 o f bosque seco premontano and bosque seco
montano bajo, respectively (Anonymous 1978a).
Because o f their location in deep valleys in the
rain shadow o f the western Cordillera, and their
floristic composition, these vegetation types correspond partly to the "inter-andean semi-deserts" described by Harling (1979). They also
correspond to the formaciones xerofflicas de los
varies interandinos [xerophilous formations of the
inter-andean valleys] described by Acosta-Solis
(1965) for the valleys o f Rio Chota, Gayllabamba, Patatr, Yunguilla-Jubones, Malacatos and
Vilcabamba. This vegetation type includes thickets of small trees o f Leguminosae-Cesalpinoideae, Bignoniaceae and Annonaceae, Agave sp.,
Gynerium sp. (ca~a brava), with small shrubs of
Compositae (Bidens sp.), Begoniaceae, and Solanaceae (Fig. 3a-c). Other herbs include representatives o f Leguminosae (Teramnus sp., Macroptilium erythroloma), G r a m i n e a e , a n d
Bromeliaceae. All populations were found on
evolved volcanic ashes or soils derived from andesites, which were brownish, well-drained, and
sometimes stony. Rainfall at collection sites was
estimated at 500-800 mm/year, with a mean
temperature 16-22~ (Anonymous 1 9 7 8 b ) a n d
driest period around July-August (Fr~re, Rijks,
and Rea 1975).
The distribution o f wild c o m m o n bean on the
western slope o f the Andes in northern Peru corresponds to the Yunga Marftima (Pulgar Vidal
1987), a typical transition zone of slopes and hills
between the coastal desert areas and the more
humid western highlands. The vegetation includes small trees and thickets the height and
abundance o f which highly depend on moisture
availability (temporary streams, favorable topography) (Fig. 3d). It could be defined as dry to
deciduous low montane tropical shrub (part of
the monte ribereho after Ferreyra 1983; or bosque
seco montano bajo tropical after Anon. 1976).
Moisture availability decreases from east to west
and from Piura in the North to southern Cajamarca in the South, which m a y explain the difference in altitude between the collections of wild
bean in Piura and in Cajamarca. The following
genera were observed: Schinus molle (a multipurpose tree, often present where wild beans are
observed in Peru), Cereus sp., Agave sp. (both
present in drier habitats), Prosopis sp., Acacia
sp., Tecoma sp., Bombax sp., Capparis sp., Cesalpinia sp. (frequently C. tara, important as fuelwood), Heliotropium sp., Lantana sp., Croton
sp., Bougainvillea sp., and Ipomoea sp. Annual
grasses (with the exception o f Gynerium sagittatum, ca~a brava, along river beds) and Compositae were also frequent. More details are given
by Ferreyra (1983) and Weberbauer (1936, 1945).
416
ECONOMIC BOTANY
[VOL. 47
Fig. 3. a) Wild common bean population DGD2762 collected on June 21, 1989, near E1 Salado (1990 masl),
Gir6n, Azuay, Ecuador. Mature plants in secondary thickets with Bignoniaceae and Compositae. Dry pods are
visible in the center of the picture. Locally called "poroto de monte." Whereas about 10 plants in this population
were seen in 1989, a second visit in 1990--a drier year in that part of Ecuador--did not reveal any plants,
suggesting important year-to-year variations in population sizes depending on weather conditions, b) Wild
common bean population DGD2769 collected on June 16, 1990, near Pepinales (2050 masl), Rio Sunticay,
Alausi, Chimborazo, Ecuador. Detail of bird damages and anthracnose symptoms on dry pods. A split and
twisted pod beak with fibers of the pod sutures and two anthracnose spots are visible on the right and left pod,
respectively, in the center of the photo. Wild birds (most probably of the dove family) eat the developing seeds
out of the young pods by opening around the beak, hence, the local name "frijol de paloma" (pigeon bean), c)
Wild common bean population DGD2769 collected on the same date and place as above. Close-up of a young
blooming plant in the middle of a seed-setting population. An open flower is visible in the center of the photo.
1993] DEBOUCKET AL: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
Mean temperature was estimated at about 18~
(13"C-25~ (for Huancabamba; FrSre, Rijks, and
Rea 1975). Precipitation of 319 mm/year for
Huancabamba (Fr~re, Rijks, and Rea 1975) was
recorded, although precipitations of up to 700
mm/year have been recorded in other places
where wild beans have been discovered. The driest period is around July-August. Part of the
precipitation might be as mists in some places
as evidenced by the presence of a few Tillandsia
sp. hanging on trees.
GENETIC EROSION AFFECTING WILD
COMMON BEAN POPULATIONSIN
NORTHWESTERN SOUTH AMERICA
The wild bean populations identified in this
study were all subjected to marked genetic erosion. For example, the habitat of the Ecuadoran
wild bean populations is being destroyed by continued agricultural expansion such that these
populations only persist on steep roadsides where
access by farmers and grazing animals is restricted. Figure 2 shows a panoramic view of the collection site of accession DGD2769 (G23582) near
Pepinales, on the road to the town of Huigra,
Department of Chimborazo, Ecuador. In this site,
wild beans were distributed between 1400 and
2000 m exclusively along roadsides and were
surrounded by fields, among them bean fields.
These small populations probably represent relics of a more abundant and widespread population prior to encroachment by agriculture.
PHASEOLIN AND ALLOZYME
VARIABILITYOF WILD MATERIALS IN
WILD P. VULGARIS OF ECUADOR AND
NORTHERN PERU
Accessions of wild P. vulgaris from Ecuador
and northern Peru were analyzed for phaseolin
seed protein and isozymes to complement the
information obtained previously for wild materials from other regions (Gepts et al. 1986; Gepts
and Bliss 1986; Koenig and Gepts 1989; Koenig,
417
Singh, and Gepts 1990). These accessions exhibited the T phaseolin type described previously
by Koenig, Singh, and Gepts (1990) for accession
DGD 1962 (G21245) from northern Peru. All accessions of this region were homogeneous for this
phaseolin type, except accession DGD2763
(G23580), which showed both 'I' and 'T' phaseolins (Table 3).
The same accessions were analyzed for the isozymes diaphorase (DIAP, E.C. 1.6.4.3), leucine
aminopeptidase (LAP, E.C. 3.4.11.1), malic enzyme (ME, E.C. 1.1.1.40), malate dehydrogenase
(MDH, E.C. 1.1.1.37), peroxidase (PRXC, E.C.
1.11.1.7), ribulose bisphosphate carboxylase
(small subunit: RBCS, E.C. 4.1.1.39), and shikimate dehydrogenase (SKDH, E.C. 1.1.1.25).
All accessions were highly homogeneous with the
exceptions of accession DGD2881 (G23724) displaying alleles 100 and 105 of locus Diap-2 and
accession DGD2788 (G23583) displaying alleles
95 and 100 of locus Diap-1. At the Me, Prxc,
Rbcs, and Skdh loci, alleles characteristic of the
Middle American gene pool were observed, with
the exception of accessions DGD1956 (G21244)
and DGD 1962, which showed the Andean allele
at the Prxc locus, and accession DGD2763, which
showed an Andean allele at the Me locus. Alleles
at the Diap-t and Lap-3 loci were those typical
for Andean germplasm, with the exception of
accessions DGD2881 and DGD2788, which displayed Middle American alleles at the Diap-I
locus. At the Mdh-I and Mdh-2 loci, all accessions exhibited the I00 allele exhibited by most
Middle American and Andean common bean
germplasm. At the Diap-2 locus, two accessions,
DGD2881 and DGD2769 (G23582), showed the
105 allele previously identified only among cultivated materials belonging to race Middle
America (Singh, Gepts, and Debouck 1991).
A principal component analysis (Fig. 4) of the
isozyme gene frequencies observed among these
wild beans from Ecuador and northern Peru,
jointly with isozyme gene frequencies observed
Late and heavy showers may sometimes cause some seeds dispersed early (or dispersed in previous years) to
germinate prematurely in spite of seed dormancy. Whereas these plants have a low probability of reaching
maturity, plant collectors can use them to establish herbarium voucher specimens and collect associated microorganisms such as Rhizobium or pathogens, d) Wild common bean population DGD2788 collected on July
27, 1989, 1km W of Santa Rosa (920 masl), Canchaque, Huancabamba, Piura, Peru. It is one of the northernmost
populations of wild common bean on the western Pacific range of the Andes in Peru and also one found at the
lowest altitude. It is called locally "frijol de paloma'" for the same reason as in 3b.). It is consumed by farmers
as emergency food when crops fail. Populations are threatened by encroaching coffee plantations.
418
Fig. 4.
ECONOMIC BOTANY
[VOL. 47
Principa•c•mp•nentana•ysis•fis•zymediversityinwi•dPhase•lusvu•garis.M•DDLEAM.:Midd•e
A m e r i c a n ; E C D + N. PER: Accessions from Ecuador a n d n o r t h e r n Peru. Data for the Middle A m e r i c a n a n d
A n d e a n accessions were obtained by Koenig a n d Gepts (1989) a n d those for the Ecuadoran a n d n o r t h e r n P e r u v i a n
accessions in this study.
TABLE 3. PHASEOLIN AND ALLOZYME CONSTITUTION OF WILD P H A S E O L U S V U L G A R ~ FROM ECUADOR
AND NORTHERN PERU.
Accession
Phs
Skdh
Rbcs
Lap-3
Mdh- 1
Mdh-2
Prxc
Me
D:ap-1
Dtap-2
G23724
G23726
G21244
G21245
G23579
G23580
G23581
G23582
G23583
G23584
G23585
I
I
I
I
I
I, T
I
I
I
I
I
103
103
103
103
103
103
100
103
103
103
103
100
100
100
100
100
100
100
100
100
100
100
103
103
103
103
103
103
103
103
103
103
103
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
98
100,98
100
100
100
100
100
100
100
102
102
102
102
102
98
102
102
102
102
102
95
102
100
100
100
100
100
100
100,95
100
100
105,100
100
100
100
100
100
100
105
100
100
100
Evolutionary
ofi~n of
predominant
allele a
M
M
M
A
--
--
M
M
A
--
a M = Middle American;A ffi Andean; -- = unmformauve (Koenl8 and Gepts 1989; Singhet al. 1991).
1993] DEBOUCK ET AL.: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
for wild bean populations from other regions (as
described by Koenig and Gepts 1989), reveals
that the wild beans o f Ecuador and northern Peru
display an intermediate position between the
Middle American and Andean gene pools consistent with their intermediate geographic location (Fig. 1). Variation along the first three principal components accounted for 35%, 19%, and
13% of the total variation, respectively. Discrimination along the first principal component was
accounted for by variation at loci Lap-3, hie,
Skdh, and Rbcs and along the second principal
component by variation at loci Prxc, Me, and
419
bia (Cundinamarca), on the western slope of the
Andes in Ecuador and in northern Peru, as well
as those discovered further south in Peru (Junin,
Apurimac, Cuzco), Bolivia and Argentina (see
Gepts and Debouck 1991; Toro, Tohme, and
Debouck 1990, for more geographical information about the full range) display the same overall
ecological habitat of the Middle American populations of wild c o m m o n bean (Delgado Salinas,
Bonet, and Gepts 1988). Throughout this distribution, the adaptive significance o f photoperiod
sensitivity may lie in the timing o f flowering such
that maturation of the plant will generally take
Skdh.
place during the dry season. Maturation during
the rainy season or in areas without dry season
will lead to seed germination inside the unopened
ALTITUDINAL DISTRIBUTION OF
pods and thus to a significant reduction in fitness.
CULTIVARS OF MIDDLE AMERICAN AND
The observation by Briicher (1989) that the
ANDEAN ORIGIN IN THE UPPER MAGDALENA
South American wild c o m m o n bean is an auVALLEY OF COLOMBIA
As shown by previous phaseolin analyses thentic component o f the mesophytic cloud for(Gepts and Bliss 1986), beans of both Middle est or rnonta~a holds true inasmuch as there is
American and Andean origin are grown in the a dry period of at least three months per year.
southwestern half o f Colombia. In the Upper In addition, in certain parts o f its range in South
Magdalena Valley (Departments ofCauca, Huila, America, wild P. vulgaris does enter into drier
and Tolima), beans are grown over a range of habitats, as seems to be the case in Loja in Ecaltitudes between the valley bottom and the pied- uador and in Piura in northern Peru. It is not
mont of the Central and Eastern Cordillera o f abundant where mist is frequent and abundant
the Andes. We used phaseolin as a marker of as in the Ceja de Selva in the Departments o f
evolutionary origin to determine whether beans Amazonas and San Martin in Peru, perhaps beo f the two major gene pools were grown at dif- cause of excessive disease pressure. It is not presferent altitudes within the same region. Cultivars ent either where rainfall is less that 400 m m /
with a Middle American phaseolin type were col- year, and thus is absent on the Peruvian coast
lected at altitudes ranging between 1040 m and south of the Santa valley.
Compared to its distribution range in Central
1840 m (average = 1523 m), whereas cultivars
America
and Mexico, and in the southern Andes
with an Andean phaseolin type were grown at
(central
and
southern Peru, Bolivia), wild P. vulaltitudes ranging between 760 m and 2120 m
garis
has
a
relatively
narrow distribution in Ec(average = 1788 m) (Table 2). A Student t-test
o f the two average altitudes shows that this dif- uador and northern Peru. This may be because
ference is significant (t = 2.33 > to 975,34df 2.03). its ecological niche is itself fairly narrow compared to its niche in other regions. Indeed, the
Andes mountain range is considerably narrower
DISCUSSION
near the Equator. The intramontane valleys on
WILD P. VULGAmS FROM ECUADOR AND
the western slope of the Andes range in Ecuador
NORTHERN PERU
and northern Peru in which wild bean populaWild c o m m o n bean is a vine of the (semi) dry tions are found constitute a very characteristic
montane tropical forest. Although it may have environment for wild c o m m o n beans. They are
originated as a perennial, it shows a strong ten- protected from the direct effects of the Pacific
dency to behave as an annual. It colonizes hab- Ocean moisture and they are characterized by a
itats where patterns of rainfall are such that the mesic temperature regime associated with their
end of the rainy season coincides with the end intermediate altitude. Other areas in this region
o f the blooming period and start of pod filling lack one or the other o f these environmental re(Growth stage R8; Gepts 1987). In that sense, quirements.
populations identified in central eastern ColomBased on these environmental considerations,
=
420
ECONOMIC BOTANY
it is possible to propose additional areas that
have not yet been collected but may still yield
wild P. vulgaris materials. The typical vegetation
type in which wild common bean is distributed
on the western slope of the Andes in northern
Peru (bosque seco montano bajo tropical) becomes very rare south of the valley of the Rio
Jequetepeque (around 7~
Lat.). Nevertheless, according to the map published by ONERM
(Anonymous 1976), and taking into account the
altitude requirements of wild common bean (9002000 masl for this area), one area still to be explored is the upper valley of Rio Chicama at the
border between the Departments of Cajamarca
and La Libertad, along the upper Rio Chuquillanqui and Rio Huancay in La Libertad. Another
possible site might be located in the upper Rio
Tablachaca close to Santiago de Chuco in La
Libertad, although its altitude might already be
too high for wild P. vulgaris. There is a reasonable possibility that wild common bean is also
distributed in the upper Marafion valley in the
Department of La Libertad, provinces of Pataz
and S~nchez Carrion, where small portions of
the subhumid montane forest are still present
(Fig. 1), thus, forming the transition to the distribution on the eastern slope of the Andes (Fig.
1). According to available data (Toro, Tohme,
and Debouck 1990), the distribution of wild
common bean south of this region resumes in
the department of Huanuco. Finally, it appears
from Fig. 1 that the area covered by the subhumid montane forest is rather small and fragmented. It is also under increasing pressure because of expanding human activities and
disturbances. Some populations of wild P. vulgaris in this region should perhaps be maintained
in in situ genetic nature reserves.
At the biochemical level, wild P. vulgaris accessions from Ecuador and northern Peru show
a combination of Middle American and Andean
alleles. The 'I' phaseolin, characteristic of this
group of accessions, lacks the 52 kD polypeptides
found in all phaseolin types in southern Peru,
Bolivia, and Argentina. Colombian wild P. vulgaris accessions, which fall in the Middle American group based on isozyme data (Koenig and
Gepts 1989), also lack the 52 kD polypeptides.
At four of the isozyme loci, these materials
showed an allele characteristic of the Middle
American gene pool, whereas at two other loci.
Andean alleles were displayed (Table 3). The intermediate nature of these accessions at the bio-
[VOL. 47
chemical level correlates with their intermediate
geographic location between the Middle American and Andean groups.
Two explanations can be put forward to account for the biochemically and geographically
intermediate nature of the wild P. vulgaris accessions of Ecuador and northern Peru. First,
they might constitute hybrids between the Middle American and Andean gene pools. An initial
cross may have led to recombinant material
adapted to the particular conditions prevailing
on the western slope of the Andes in Ecuador
and northern Peru. Second, these populations
represent relics of an ancestral P. vulgaris type
from which the two major branches--Middle
American and Andean--gradually diverged and
were dispersed. Khairallah, Adams, and Sears
(1990) found a significantly higher diversity for
mtDNA in the one accession from northern Peru
(DGD 1962) included in their study, in comparison to the mtDNA in the Middle American and
Andean gene pools. It may be interesting in this
respect to perform a phylogenetic analysis of the
Middle American and Andean phaseolin types,
as well as the 'I' phaseolin type, to establish a
phylogeny of various segments of the P. vulgaris
germplasm and estimate a time of divergence
between the Middle American and Andean gene
pools.
Two wild accessions from Ecuador showed the
Diap-2 ~~ allele. Prior to this study, this allele
had only been described in cultivated P. vulgaris,
more specifically in race Mesoamerica of the
Middle American gene pool (Sprecher 1988;
Singh, Gepts, and Debouck 1991). The presence
of this allele among wild common beans of Ecuador and northern Peru may be due to the presence of occasional outcrosses with cultivated genotypes carrying the Diap-21~ allele. Cultivars
of race Mesoamerica are relatively more frequent
in the northwestern part of South America (Singh,
Gepts, and Debouck 1991). Alternatively, the
presence of this allele among cultivated genotypes could be explained by gene flow from wild
populations either in Ecuador or in other regions
of the Middle American gene pool. A direct domestication appears unlikely because of the absence of the T phaseolin type among cultivated
genotypes. However, it may be worthwhile reexamining the cultivated gene pool for the presence of this phaseolin type.
Finally, the significance of these wild P. vulgaris populations is threefold. First, no record
1993] DEBOUCK ET AL.: PHASEOLUS VULGARIS IN NORTHWESTERN SOUTH AMERICA
was available prior to 1989 about the presence
o f these populations in Ecuador in spite of the
importance o f c o m m o n bean in the economy and
the nutrition o f this country. This suggests that
the precise boundaries o f the distribution o f the
wild ancestor o f c o m m o n bean are still imperfectly known and that additional explorations are
necessary to collect the wild ancestor o f c o m m o n
bean. For other crops, particularly those for which
the ancestor is still unknown (e.g., faba bean, B
genome donor o f bread wheat), additional explorations m a y also be useful. Second, the potential importance o f wild c o m m o n bean populations in northern Peru and Ecuador was
realized based on analysis o f molecular markers.
This illustrates the effectiveness a dynamic interplay between exploration and genetic diversity
analyses at the molecular level can have to focus
the efforts o f genetic conservation activities on
truly distinct segments of the germplasm. Third,
the intermediate nature o f these materials m a y
be o f interest to breeders who have had trouble
recombining the two major gene pools. These
materials represent stable and fit genotypes combining alleles o f both gene pools. They constitute
study materials to determine which regions of
the genome can be recombined and could constitute bridging materials to transfer genetic diversity between the two major gene pools if this
cannot be achieved by direct crosses.
CULTIVATED COMMON BEAN FROM THE
UPPER MAGDALENA VALLEY IN COLOMBIA
The Student t-test revealed a significant difference between the average altitudes at which
beans are grown in the U p p e r Magdalena valley,
the materials o f Andean origin being grown at
higher altitude in comparison to the Middle
American ones. The average difference in altitude o f 300 m corresponds to a difference o f at
least l~ in average temperature.
What is the cause o f this difference in altitude?
It could be argued that different cultural groups
live in these different altitudes. These groups
would show different preferences in regard to
seed type (size, color, and shape), growth habit,
etc., that distinguish the Middle American and
Andean cultivated types (Gepts et al. 1986; Singh,
Gepts, and Debouck 1991; Singh et al. 1991).
This explanation is unlikely, however, because
these cultivated materials were collected at relatively short distances within the same valley in
which the population is probably culturally ho-
421
mogeneous. An alternative explanation is that
this altitude difference is due to a genuine difference in average adaptation between cultivars
o f the Middle American and Andean gene pools
in this region. It then remains to be determined
which biological phenomena are most affected
by this difference in adaptation. Wild c o m m o n
bean from the southern Andes has larger seeds
compared to its Middle American counterpart.
In addition, cultivated genotypes o f the Andean
gene pool also have larger seeds than the Middle
American cultivated genotypes (Gepts et al. 1986;
Gepts and Debouck 1991; Singh et al. 1991). One
could argue that the larger seeds o f Andean materials allow them to germinate and compete with
weeds at lower temperatures (according to a scenario proposed earlier, Debouck 1987). Over the
long term, this speedier or more uniform germination could confer a comparative evolutionary advantage in the Andes not only in natural
environments but also cultivated environments.
Several agricultural groups in the Andes practice
a potato and other tuber-based agriculture and
live at altitudes higher than agricultural people
in Middle America. In the Middle American gene
pool o f c o m m o n bean, races 'Durango' and 'Jalisco' selected for the highlands o f Mexico have
comparatively larger seeds than race 'Mesoamerica' distributed predominantly in the warmer
lowlands o f Mexico and Central America (Singh,
Gepts, and Debouck 1991). Cultivated lima bean
o f the Andes has larger seeds than cultivated lima
beans of the Middle American group (Erickson
1982; A. Maquet, D. Debouck, and P. Gepts,
unpublished research). For a crop introduced into
the Andes like maize, a similar selection towards
larger grains was made in certain cases, e.g., the
race 'Cuzco' (Bird 1984; Cutler 1946; G o o d m a n
and Bird 1977; Kaplan 1956).
The larger seed size o f cultivars may not be
due only to selection for adaptation to particular
environmental conditions. H u m a n selection on
esthetic grounds for larger seeds may also account for part o f the seed size differences between
Middle American and Andean beans. In addition, other unrecognized factors m a y also be responsible for the difference o f adaptation. Further confirmation o f this difference in adaptation
m a y come from measurements o f productivity
in reciprocal plantings o f Middle American and
Andean genotypes. For both groups ofgenotypes,
a sufficiently large sample will have to be used
in order to account for the range o f adaptations
422
ECONOMIC BOTANY
within each group as suggested by the presence
o f native landraces with Andean phaseolin types
and grown at low altitudes (e.g., DGD2942).
In summary, the explorations and subsequent
laboratory analyses on which we report here have
provided a wealth o f additional information
about the organization o f genetic diversity. We
have been able to identify an important heretofore unreported segment o f the c o m m o n bean
germplasm that will help us understand the origin of P. vulgaris and the transfer o f genes between the two major gene pools of the species.
We also provided evidence that the cultivars o f
the two gene pools may have inherently different
adaptations, more specifically that on average the
Andean gene pool is adapted to slightly cooler
temperatures than the Middle American gene
pool.
ACKNOWLEDGMENTS
The exploration and laboratory analyses were funded by the Umted
States Department of Agriculture and the International Board for Plant
Genetic Resources. Additional assistance was provided by the Instltuto
Naoonal de Investlgaclones Agropecuanas (INIAP, Qulto, Ecuador), the
Instltuto Colomblano Agropecuano (ICA, Santaf6 de Bogot,q, Colombia)
and the Genetic Resources Umt of the Centro Internaoonal de Agrlcultufa Tropical (Cah, Colombia). We thank M Iwanaga, R. Hannan, Lois
Lrpez, Nelson Diaz, Pablo Pmtado, Rafl Castdlo, Onth Youdovlch, and
Alora Arias for support at various stages of this research.
LITERATURE CITED
Acosta-Solis, M. 1965. Los recursos naturales del
Ecuador y su conservacirn, 1ra parte. Instituto Panamericano de Geografia e Historia, Mrxico, D.F.
Anonymous. 1976. Mapa ecolrgico del Peril, 8 hojas,
escala 1,000,000. Oficina Nacional de Evaluaci6n
de Recursos Naturales (ONERM) and Instituto
Geogr~fico Militar, Lima.
9 1978a. Mapa ecolrgico, escala 1:1,000,000.
Ministerio de Agricultura y Ganaderia, Pronareg,
Instituto Geogr~fico Militar, Quito, Ecuador.
9 1978b. Mapa bioclim~itico, 1 hoja, escala
1:1,000,000. Ministerio de Agricultura y Ganaderia, Pronareg, Instituto Geogr~fico Militar, Quito,
Ecuador.
9 1982. Atlas regional andino. Instituto Geogr~tfico 'Agustin Codazzi', Bogot~t.
--.
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